Treatment of paraffinic fractions



3,322,843 PARAFFINIC FRACTIONS The present invention is directed to treatment of paraffins containing small quantities of contaminants. More particularly, the invention is concerned with treatment of normal paraflinic fractions containing trace amounts of contaminants. In its more specific aspects, the inven- 3,322,843 Patented May 30, 1967 Although Table I shows typical inspection characterice . istics and analyses of the feed and product, it is not intended that the invention be confined to such specific feeds, or to feeds containing the specific contaminants or specific amounts of the contaminants.

As a general statement, the parafiinic hydrocarbon fraction may suitably boil Within the range from about 250 F. to about 650 F. Preferably, the parafiinic hydrocarbon may boil within the range from about 400 F. to about 600 F.

The catalyst employed in the practice of the present invention is suitably a Group VI metal catalyst, such as chromium, molybdenum, and tungsten; while the Group VIII metal catalyst may include iron, cobalt, nickel, paltion is concerned with treatment of paraflinic hydrocarl5 ladium, and platinum. bons in the presence of hydrogen to remove contaminat- When these catalysts are employed in the practice of ing compounds. the present invention, they may be used as the oxides The present invention may be briefly described as a supported on a suitable support, such as alumina. For method for treating a paraflinic hydrocarbon fraction havexample, the catalyst may be termed cobalt molybdate, ing 9 to 20 carbon atoms in the molecule, which is con- 20 which is a mixture of oxides of cobalt and molybdenum. taminated with polar compounds, such as phenols and Ordinarily, the catalyst, such as cobalt molybdate, may carbonyls, and with unsaturated hydrocarbons, such as contain from about 2% to about 10% by weight of cobalt olefins and aromatics, and may be contaminated also with oxide, and about 10% to about by Weight of moly-bsulphur, color bodies, nitrogen and the like. In the practice denum trioxide on alumina. Small amounts of sodium of the present invention, the contaminated fraction is oxide, iron and silicon dioxide may be present. The socontacted in the presence of free hydrogen with a catalyst called molybdate may be pretreated prior to employment, such as a Group VI or Group VIII metal or a mixture of such as by sulfiding with a 0.4% by weight solution of Group VI and Group VIII metals. The Group VI and carbon disulfide in normal hexane at a temperature of Group VIII metals are the metals in the Periodic Ar- 625 F. and 560 p.s.i.g. pressure at about 1 v./v./hr. in rangement of the Elements by Mendeleefi, found on page the presence of about 750 s.c.f of hydrogen 308 of the Handbook of Chemistry and Physics, 25th ed., The Group VIII metal oxides, such as nickel oxide, Chemical Rubber Publishing Co., Cleveland, 1941. The may also be suitably pretreated with a hydrogen gas contacting operation is conducted at a temperature within mixture or a hydrogen-rich gas. Ordinarily, the Group the range of about 300 F. to about 400 F. when the VIII metal, such as nickel, may be present in an amount catalyst is a Group VIII metal; and the contacting is conof about 2% to about 60% by Weight of active nickel on ducted at a temperature within the range of about 500 F. a suitable support, such as kieselguhr or alumina. to about 750 F. when the catalyst is a Group VI metal In practicing the present invention, the fraction being or contains a Gro-upVImetal. treated may be passed over the catalyst arranged in a The parafiinic hydrocarbon fraction is preferably a norsuitable bed at temperatures within the range of about mal paraflin fraction which is obtained by separating nor- 300 F. to about 400 F. when the catalyst is a Group mal paraflins from its mixtures with other hydrocarbons, VIII metal, such as nickel. The parafiin hydrocarbon may such as isoparafiins and the like, using a molecular sieve also be contacted with the catalyst suspended in it as as an adsorbent. Separation of normal parafiins from isoa slurry, or the so-called fluidized solids technique may paraffins employing molecular sieves is a Well-known be used in the contacting operation. When the catalyst process and further details thereof need not be given here. is a Group VI metal or a mixture of a Group VI metal However, the product produced from such a process may and a Group VIII metal, the fraction may be contacted contain contaminating compounds which interfere with with the metal arranged in a bed at a temperature withthe use of the product, particularly Where the paraflin is in the range of about 500 F. to about 750 F. Regardemployed as a feedstock to an alkylation process for proless of the catalyst employed, a space velocity within the ducing biodegradable detergent alkylates. As an example range of about 0.5 to about 5.0 volumes of p-arafiin hyof the contaminating compounds, reference is had to drocarbon per hour per volume of catalyst is charged. Table I where typical inspection characteristics and anal- Pressures are within the range of about '500 to about yses are given of a C to C a paraflinic feed and product 1000 p.s.i.g. The amount of hydrogen employed is suitfed into and recovered from a treating operation in acably from about 200 to about 2000 s.c.f. of hydrogen cordance with the present invention. per barrel of the fraction.

TABLE I Products O11-C14 Parafim Feed Nickel Cobalt Molybdate .APHA 1 color 0 15 0 0 APHA colorhold (16 hrs. at 212 F.) 15 30 0 0 Wt. percent olefins 0.333 0. 360 0. 039 0.037 Wt. percent aromatics" 1.1 1. 3 0.0 0.27 P.p.m.phen0ls 550 670 3.4 0.9 P.p.m. thiophenols 12 21 0.7 0. 1 I.p.m. carb0nyls. 17 21 0.0 0. 0 P.p.m. total nitrogen 7 12 0. 0 1.0 Ppm. total sulphur 17 20 1. 0 1. 0

1 American Public Health Association.

The present invention involves a molecular sieve operation where virgin petroleum naphtha fractions, such as those having 9 to 20 carbon atoms, are treated to separate normal paraffins from other hydrocarbons. The normal paraffin fraction may then be suitably distilled in a fractional distillation zone to produce a fraction such as one having from about 11 to 14 carbon atoms and predominately normal paraffins. These fractions then may be treated with hydrogen over the Group VIII metal catalysts on a support, such as alumina, or over a supported Group VI metal catalyst.

Suitable conditions for use with a catalyst mixture of a Group VIII metal catalyst and a Group VI metal catalyst, such as cobalt molybdate, are as follows: a

temperature of 625 F., a pressure ranging from about 350 to about 660 p.s.i.g., a space velocity of 0.5 to 4 volumes of liquid per hour per volume of catalyst, and 750 s.c.f. of hydrogen per barrel of liquid feed.

Conditions suitable for use where a Group VIII metal catalyst (such as a nickel catalyst) is used include a temperature from about 300 F. to about 400 F., a pressure of about 660 p.s.i.g., a space velocity of about 0.5 to about 4 volumes of liquid per hour per volume of catalyst, and 750 s.c.f. of hydrogen per barrel of liquid feed.

While it is preferred to use a sequence where the paraffinic fraction is subjected first to molecular sieve separation, and is then fractionally distilled and then contacted with free hydrogen in the presence of a catalyst, it is contemplated that the fractional distillation step may 'follow the hydrogen treating step whereby several streams of improved quality which are substantially free from contaminants may be obtained. Likewise, the molecular sieve separation step may follow the fractional distillation step or the hydrogen treatment step, or both of these steps. It will be preferred, however, to use the hydrogen treatment step after the molecular sieve separation and optionally before or after fractional distillation.

In order to illustrate the present invention further,

normal parafiin fractions produced in a sequence involv-' ing molecular sieve separation, fractional distillation, and hydrogen treatment in accordance with the present invention, is compared with the products resulting from treatment of paraffins from a molecular sieve operation with an adsorbent such as Por-ocel and with strong sulfuric acid, such as olenm. The following Table II'presents a comparison of these several operations:

invention and the performance of the product in the :present invention is superior to that of the prior art treatments. The performance characteristic or number is a measure of the satisfactory utilization of the paraffin on alkylation and thus is indicative of the quality of the product.

The present invention is quite important and useful in that it is possible to produce pure paraffinic hydrocarbons which are eminently suitable for production of biodegradable detergents. The product of the present invention may be used for other purposes where pure paraffins are required, such as diluents for catalytic reactions, solvents employed in foodstuff processing operations, paint thinners, dry cleaning solvents, and the like.

The nature and objects of the present invention having been completely described and illustrated and the best mode contemplated set forth, what We wish to claim as new and useful and secure by Letters Patent is:

1. A method for obtaining a substantially pure normal paraffin fraction which comprises treating a parafiinic hydrocarbon fraction containing paraffins and isoparaffins with a molecular sieve to separate and recover from said paraffinic hydrocarbon fraction a normal paraffin fraction which is contaminated with phenols, carbonyls, olefins, nitrogen, sulphur, color bodies, and aromatics, and then contacting said normal parafiin fraction with a catalyst selected from the group consisting of Group VI and Group VIII metals and mixtures of Group VI and Group VIII metals in the presence of free hydrogen under suitable temperature conditions to substantially remove said contaminants and to form a purified product.

2. A method in accordance with claim 1 in which the Group VIII metal is nickel and the Group VI metal comprises molybdenum.

3. A method in accordance with claim 1 in which the normal paraffin fraction is fractionally distilled prior to said contacting.

4. A method in accordance with claim 1 in which the normal paraffin is fractionally distilled subsequent to said contacting.

5. A method in accordance with claim 1 in which the catalyst is nickel.

6. A method in accordance with claim 1 in which the catalyst is cobalt molybdate.

7. A method in accordance with claim 1 in which the normal paraflin fraction contains 11 to 14 carbon atoms.

TABLE IL-ANALYTIOAL AND PROCESSABILITY DATA OF C r-C14 NORMAL PARAFFINS Wt. Percent Item Phenols, Car'bcnyls, Olefins, Nitrogen, Sulphur, Aromatics Performance, No. Description of Treatment ppm. p.p.m. Wt. p.p.m. p.p.m. Avg. Percent Percent U.V. M.S.

1 Nickel hydrogenation, 2 v./hr./v. 750 s.e.f./ 3. 4 0. 0 0. 039 0 2 0. 0 0. 0 -l00 bbl. H 350 F., 660 p.s.i.g. 2 Cobalt molybdate hydrogen treating, 2 0.9 0 0.037 1 1 0.27 -100 v./h r./v., 750 s.c.f./hbl. H 625 F., 660 p.s.i.g. 3 Porocel pereolated, 5 v./v., 20/60 mesh 0. 5 0.0 0.219 1 3 0.1 0.8 98. 3 4 0 -01 10 lb./bbl. eleum treat, followed 12 13 0.180 4 0.4 0. 5 -97 by 011-014 heart cutting. .5 Untreated. 650 20 0.333 11 20 1.3 1.4 86.8

1 Weight ppm. as an average molecular weight phenol. 2 Carbonyls as weight p.p.m. 0:0. 3 Olefins by Bromine Index, ASTM D1491 plus Benzene.

4 Total nitrogen, modified Kjeldahl on acid extract from 200 gram sample.

5 Relative scale as a function of conversion and yield on alkylation.

8. A method in accordance with claim 1 in which said contacting is conducted at a space velocity within the range of about 0.5 to about 5 volumes of normal parafiin per hour per volume of catalyst, at a pressure within the range of about 500 to about 1000 p.s.i.g., and in the presence of about 200 to about barrel of said fraction.

9. A method in accordance with claim 1 in which the catalyst is supported on alumina.

10. A method in accordance with claim 1 in which the purified product is fractionally distilled to recover a fraction having 11 to 14 carbon atoms.

11. A method in accordance with claim 1 in which the metal is selected from Group VIII and the contacting is conducted at a temperature within the range of about 300 to about 400 F.

12. A method in accordance with claim 1 in which the metal is selected from Group VI and mixtures of Group VI and VIII and the contacting is conducted at a temperature within the range of about 500 F. to about 750 F.

13. A method in accordance with claim 1 in which the normal parafiin fraction contains 9 to 20 carbon atoms in the molecule.

14. A method for obtaining a substantially pure nornal paraffin fraction which comprises treating a paraflinic hydrocarbon fraction containing parafiins and isoparafiins with a molecular sieve to separate and recover from said paraflinic hydrocarbon fraction a normal paraffin fraction having 9 to 20 carbon atoms in the molecule which is contaminated with carbonyls, olefins, nitrogen, sulfur, color bodies, and aromatics, and then contacting said fraction with a catalyst selected from the group consisting of the Group VI metals and mixtures of Group VI and Group VIII metals in the presence of free hydrogen at a temperature within the range of about 500 F. to

2000 s.c.f. of hydrogen per about 750 F. to substantially remove said contaminants and to form a purified product.

15. A method for obtaining a substantially pure normal paraffin fraction which comprises treating a paraffinic hydrocarbon fraction containing parafiins and isoparafiins with a molecular sieve to separate and recover from said paraflinic hydrocarbon fraction a normal parafiin fraction having 9 to 20 carbon atoms in the molecule which is contaminated with carbonyls, olefins, nitrogen, sulfur, color bodies, and aromatics, and then contacting said fraction with a catalyst selected from the Group VIII metals in the presence of free hydrogen at a temperature within the range of about 300 F. to about 400 F.

References Cited UNITED STATES PATENTS 1,973,833 9/1934 Wietzel et al 260--676 2,073,578 3/1937 Gwynn 208-217 2,121,998 6/1938 Tilton 260 -676 2,134,333 10/1938 Jahrstorfer et a1. 260-676 2,436,923 3/1948 Haensel 260676 2,560,415 7/1951 Cornell 208-217 2,587,987 3/1952 Franklin 208217 2,900,322 3/ 1956 Northcott et al 208-216 2,921,022 1/ 1960 Sowerwine 208-217 3,055,824 9/1962 Squires et a1 208217 3,242,101 3/ 1966 Erickson et a1 260667 ALPHONSO D. SULLIVAN, Primary Examiner. 

1. A METHOD FOR OBTAINING A SUBSTANTIALLY PURE NORMAL PARAFFIN FRACTION WHICH COMPRISES TREATING A PARAFFINIC HYDROCARBON FRACTION CONTAINING PARAFFINS AND ISOPARAFFINS WITH A MOLECULAR SIEVE TO SEPARATE AND RECOVER FROM SAID PARAFFINIC HYDROCARBON FRACTION A NORAML PARAFFIN FRACTION WHICH IS CONTAMINATED WITH PHENOLS, CARBONYLS, OLEFINS, NITROGEN, SULPHUR, COLOR BODIES, AND AROMATICS, AND THEN CONTACTING SAID NORMAL PARAFFIN FRACTION WITH A CATALYST SELECTED FROM THE GROUP CONSISTING OF GROUP VI AND GROUP VIII METALS AND MIXTURES OF GROUP VI AND GROUP VIII METALS IN THE PRESENCE OF FREE HYDROGEN UNDER SUITABLE TEMPERATURE CONDITIONS TO SUBSTANTIALLY REMOVE SAID CONTAMINANTS AND TO FORM A PURIFIED PRODUCT. 